Reproductive Technology: Mum, Dad And Mitomum

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Assisted reproduction is one of those rare areas in which Britain really does do world-leading research. Louise Brown, the world's first "test-tube" baby, was born in an Oldham hospital in 1978.

In-vitro fertilisation, the technique that resulted in her conception, was pioneered by Robert Edwards and Patrick Steptoe, two British doctors. In 2010 Mr Edwards was awarded the Nobel prize in medicine for his work.

Now the government is pondering another first. On June 3rd the Human Fertilisation and Embryology Authority (HFEA), which regulates assisted reproduction, opined that, as far as it could see, there was no evidence to suggest that a genetic-engineering technique called "mitochondrial transfer" was unsafe.

The technology, which was pioneered in Britain and America, is designed to cure the roughly one baby in 6,500 that would otherwise be born with a serious, untreatable mitochondrial illness. But it has caused a stir, for two reasons. Children born via the technique would have three genetic parents. And, if approved, it would be the first time that any country has allowed a genetically engineered change that could be passed on to the offspring of the person on whom it was performed.

Mitochondria are tiny structures, present in almost every cell in the body, that convert food and oxygen into energy. They are the descendants of ancient bacteria which gave up their free-living lifestyle to form a symbiotic relationship with other cells. As such, they have their own tiny genomes, independent from the DNA in the cell's nucleus. Unlike that nuclear DNA, which is inherited from a child's father and mother, every mitochondrion in a person's body is descended from those inside his mother's egg.

The idea is to give a baby (or, more exactly, a fertilised egg) with misfiring mitochondria a fresh set donated by another woman. That involves removing the nucleus of the fertilised egg (and the DNA it contains) and transplanting it into a second, donor, egg which contains properly-functioning mitochondria.

The resulting child would inherit roughly 20,000 genes-worth of nuclear DNA from its mother and father, and exactly 37 mitochondrial genes from the egg donor ("mitomum" seems to be the neologism of choice). In other words, it would inherit its genetic information from three people. And because those same donated mitochondria would find their way into a female child's eggs, the procedure would alter the DNA of her children in turn.

Three-parent babies and gene-line modifications might be expected to invite shrill headlines about "playing God". By and large, that has not happened. Britain does not go in for American-style culture wars. But part of the credit also belongs to its cautious bureaucrats. The HFEA has a reputation for thoroughness (some might describe it as overzealousness). This report on safety is the third it has issued. Even then, it recommended a few more experiments be carried out.

But thoroughness is a good thing with an experimental treatment like mitochondrial transfer, reckons Douglass Turnbull, a neurologist at the University of Newcastle and one of the pioneers of the technique. He points to the HFEA's public consultations. Most people the outfit spoke to "didn't even know what a mitochondrion was, at first," he says. "But when the technique was explained to them, most decided that the benefits outweighed the risks." And he points out that many other rich countries, lacking a specialist regulator of their own, look to the HFEA's work to inform their own laws.

The technique has both public approval and the HFEA's blessing in principle. The government has made it a priority, too: in February it published draft regulations that, if passed by Parliament, would make Britain the first country to license mitochondrial transfer in humans. Assuming no serious problems turn up at the last minute, the first three-parent babies could arrive within a couple of years.